TRIPOLI, Libya — The young militia fighters carried in a comrade who was covered in blood and motionless. It was 1:30 p.m. Friday at the Al Mokhtar Clinic, and Libya’s civil war had just reignited in this fractured capital.

“Move on, clear the way,” one fighter screamed. “He’s dying.”

Five hours earlier, on the eve of the holy Muslim fasting month of Ramadan, fierce clashes erupted between rival militias. They tore apart a two-month lull in the violence and upended the lives of countless Libyans in neighborhoods that turned into battle zones overnight.

The fighting also underscored the security and logistical challenges British investigators could face if they consider visiting Libya to pursue clues in the Manchester concert suicide bombing that killed 22 people this week. The bomber, Salman Abedi, was of Libyan origin, and his father and brother were arrested in Tripoli. Both are in the custody of a counterterrorism militia aligned with the Western-backed government.

Those challenges were evident during an hours-long drive Friday in a city fragmented as much by politics, ideology and geography as it is by violence and the thirst for power. In the southeastern enclaves, militias deployed tanks and used heavy artillery, leaving families trapped inside their homes and sending many civilians and fighters to hospitals with injuries. Authorities could not provide reliable casualty figures.

The renewed fighting in Libya arrived on the eve of Ramadan. (Lorenzo Tugnoli /For The Washington Post)

But in the northern neighborhoods, untouched by Friday’s violence, Tripoli residents surreally socialized in cafes and water-skied in the Mediterranean Sea, even as the sound of explosions and gunfire thundered nearby. Huge plumes of black smoke from burning buildings rose over the city.

“This has become normal for us,” said Shukri Salim, 27, a Libyan Airlines employee, who was having coffee with friends in a cafe and watching a televised soccer match.

“I knew it was Ramadan and the war is going to start,” said his friend Ayoub Aldabaa, 27, an accountant, who was with him. “We’re so accustomed to this.”

Last year, too, fighting engulfed the capital during Ramadan. That time, the clashes involved different militias.

It has been mostly like this since the 2011 populist uprising, part of the Arab Spring, that ousted Libyan dictator Moammar Gaddafi and led to his killing. A constellation of tribal and regional militias emerged, seizing advantage of the power vacuum and abundance of weapons in a quest for power and wealth.

Today, militias have carved up the oil-producing country into fiefdoms, each aligned with one of three competing governments. And Tripoli, as expected, has been a major battleground with armed groups fighting for control of neighborhoods, even streets and buildings.

Friday’s violence pitted militias aligned with the U.N.-backed Government of National Accord (GNA) against Islamist-leaning forces of the self-declared National Salvation government who are trying to reclaim territory lost in recent months, according to security officials.

A spokesman for the National Salvation government said a GNA-aligned militia erected a fake checkpoint to kidnap some of its fighters. “So we decided to attack the GNA boys,” said the spokesman, Brig. Gen. Mahmud Zaghal.

But there has also been speculation for weeks that the National Salvation militias were planning a counterattack. A Facebook page created by its supporters carried a post on Thursday night announcing that it would launch assaults against rivals in southern Tripoli.

The clashes Friday mostly unfolded in the neighborhoods of Abu Salim, Salahedeen and Al Habda. Fighting also erupted in areas near the Rixos Hotel, which has been used by officials and lawmakers aligned with the GNA government.

Last October, their new legislative body was ousted from the buildings by the Salvation militias. In December, the area was the scene of heavy fighting over several days. Militias aligned with the GNA currently are in control of the complex and surrounding neighborhoods.

“We will retake the Rixos,” Zaghal vowed.

At the Al Mokhtar Clinic, the toll of the fighting was obvious. Doctors and nurses were inundated by the wounded. One man arrived with blood splattered on his legs.

“My brother was injured,” another man said as he waited outside. “He was just standing in front of his house when the shells landed.”

But the militia fighters were most visible at the clinic.

“I want to get inside the room,” one fighter screamed, as others held him back from accosting the doctors and nurses.

At 1:53 p.m., screams filled the room. Some militia fighters cried, their faces now filled with anguish.

Their comrade had died on the operating table.

An hour later, Aldabaa and Salim were in the cafe. As they have done during previous clashes, they called friends and family around the city to make sure they were safe. They also checked Twitter and Facebook to see which neighborhoods had turned into no-go zones.

Salim had just spoken to a friend who was stuck in his home as fighters pummeled each other outside.

He and Aldabaa had both taken part in the revolution. Salim said he did not regret fighting against the Gaddafi regime, but “regretted the people who came after the revolution.”

Aldabaa blamed the Western countries for helping the rebellion that ousted Gaddafi, and now regrets that the revolution happened at all.

“We were expecting to take the country in a better direction,” he said. “Unfortunately, we left it in a worse condition.”

At 3:15 p.m. near the Rixos Hotel, militia fighters in pickup trucks waited for the next offensive. Graffiti on the wall of the complex read: “Free Libya.”

By 4:30 p.m., drivers were in lines at gas stations around the city, preparing for shortages that usually come after each clash.